Production of granular water-soluble perborate-containing salt mixtures



Feb. 21, 1961 J. SCHMIDT ETAL PRODUCTION OF GRANULAR WATER-SOLUBLE PERBORATE-CONTAINING SALT MIXTURES 2 Sheets-Sheet 1 Filed May 4, 1956 1NVENTOR JOACH/M SCHMIDT W/LHELM VOL/(AMER ATTORNEYS Feb. 21, 1961 J. SCHMIDT ETAL PRODUCTION OF GRANULAR WATER-SOLUBLE PERBORATE-CONTAINING SALT MIXTURES Filed May 4, 1956 2 Sheets-Sheet 2 INVENTOR JOACH/M SCHMIDT 1 W/LHELM VOL/(AMER BY W ATTORNEY:

PRODUCTION OF GRANULAR WATER-SOLUBLE PERBORATE-CONTAININ G SALT MIXTURES Joachim Schmidt and Wilhelm Volkamer, Dusseldorf- Benrath, Germany, assignors to Henkel 3: Cie G.m. b.H., Dusseldorf-Holthausen, Germany, a corporation of Germany Filed May 4, 1956, Ser. No. 582,886

Claims priority, application Germany Sept. 8, 1955 '14 Claims. (Cl. 252-186) This invention relates to new and useful improvements in the production of granular water-soluble perboratecontaining salt mixtures.

Perborates are frequently used in detergents and bleaching agents as oxygen-liberating materials. Since perborates are temperature-sensitive, particularly in the presence of water, they must be mixed with the detergents and bleaching agents after the liquid or paste has been converted into a powder by drying.

The commercially available borates generally are in solid, finely divided form, having a relatively small particle size. Since the particle nize of the commercially available borate is frequently about one-tenth to one hundredth that of the other components of the detergent, the same would tend to separate out upon transportation and storage.

In order to overcome this difiiculty, attempts have been made to produce perborates of low bulk weight by heating the same on hot surfaces. In this connection, however, the particles formed do not have the necessary mechanical strength, and, unless the operation is very carefully effected, there is a strong tendency of the perborates to decompose.

One object of this invention is the granulation of finely divided perborates into a more coarsely granular form, which may be mixed with detergents and bleaching agents without any tendency toward separation.

Figure 1 is a diagrammatic representation of a plant set-up for effecting the process in accordance with the invention;

Figure 2a is a diagrammatic front elevation partly in section, showing an embodiment of a granulating device for use in accordance with the invention;

Figure 2b is a diagrammatic side elevation partially in section, showing the granulating device of Figure 2a;

Figure 2c is a diagrammatic perspective view showing the granulating device of Figure 2a;

Figure 3a is a diagrammatic side elevation partially in section, showing a further embodiment of a granulating device for use in the process in accordance with the invention; and

Figure 3b is a diagrammatic front elevation showing the granulating device of Figure 3a with a portion of the drum rim cut away.

In accordance with the invention, granular salt mixtures containing a perborate which may be used in the conventional manner in detergents and bleaching agents without any tendency toward separation is formed by moving a finely divided water-soluble perborate, and preferably sodium perborate, on a support surface for contact between the individual divided particles while spraying the perborate with a thinly liquid dispersion of an undissolved salt capable of crystallizing with the inclusion of water of crystallization in an aqueous solution of a salt capable of crystallizing with the inclusion of water of crystallization at a temperature above the melting temperature of the lowest melting component of said undis- 2,972,584 Patented Feb. 21, 198i solved salt. The contact of the perborate and the dispersion is effected at a temperature which will allow crystallization of the undissolved dispersed salt and the aqueous salt solution. The salt solution spray should contain an amount of water not substantially in excess of the amount of water capable of being bound as water of crystallization by the salt mixture formed.

As a result of the process, a salt mixture forms, in which substantially all of the water sprayed is bound as water of crystallization, and in which a granular perborate salt mixture is formed, the granules of which are composed of individual, finely divided water-soluble perborate particles, such as sodium perborate particles bound together by inorganic salt crystals containing water of crystallization. The perborate is present in the mixture in amount ranging from 15% by weight trihydrate to anhydride, as, for example, in the case of sodium perborate in amount ranging from 15% NaBO .H O .3H O

to 95% by weight NaBO .H O- and preferably to 65% by weight of NaBO .H O

The perborate may be admixed with a solid divided inorganic salt, such as the same salt used in the sprayed dispersion and/or solution in calcined form prior to the spraying and there may be present in the mixture, and/or preferably in the dispersion solution the customary stabilizers for perborate compounds, such as magnesium silicate or other water-unsoluble silicates, magnesium soaps, magnesium phosphates, metastannic acid, etc.

The finely divided perborate, when the same is sprayed, may be moved in any desired manner, so that the individual particles contact each other to conglomerate, and may, for example, be sprayed in conventional rotating granulation devices. The perborate particles, however, may not be eddied or atomized in a gas stream such as air.

The perborate particles struck by the sprayed dispersion adhere to other perborate particles which have preferably not been wetted by the dispersion, and there is formed a granulate which consists of a plurality of perborate particles of original size, which are bonded together by the sprayed dispersion of inorganic salts. Since perborate particles, in the preferred embodiment of the process, are at room temperature, while the dispersion is generally sprayed at higher temperature, the dispersion solution cools down and solidifies with the formation of the solid salts which contain water of crystallization. There is thus produced a solid granulate of perborate particles of original size, which are cemented to each other, this granulate, upon being introduced into water, rapidly breaking up into the original perborate particles, due to the dissolving of the layer of inorganic salts containing water of crystallization located between or on the perborate particles, so that the entire original surface of the perborate powder is offered the water. Accordingly, these particles dissolve almost as rapidly as the non-granulated perborates of the original size.

As starting material, there is preferably used sodium perborate of the formula:

NaBO2.H2O -3H2O not restricted to the use of perborates of the indicated particle size.

The method of the invention is particularly well suited for the working of those inorganic salts crystallizing with the inclusion of water of crystallization which are of lower solubility than soda, in which connection the solubility is expressed in percentage of anhydrous dissolved substance, referred to the total solution. Of course, salt mixtures may also be employed. However, the invention is not limited solely to the use of only slightly soluble salts but can also be employed in con nection with readily soluble salts, particularly in cases where solid inorganic salts which are preferably in anhydrous state have been admixed with the perborate before it is sprayed with the solution. In accordance with the invention, these salts are dispersed in a salt solution, in which connection the dispersed salt need not be identical with the dissolved salt, and the solution and solid salt are added simultaneously, whereby a separate feeding device for the solid salt to be admixed is dispensed with. In all cases, the spray solution containing solid salts is a thinly liquid dispersion of solid salt in a preferably saturated salt solution which contains only minor quantities, i.e. less than 50% by weight and preferably less than 30% by weight of solid salt referred to the entire dispersion and can be considered practically as liquid.

The quantity of dispersion to be sprayed, which is preferably employed at elevated temperature is dependent, inter alia, on the particle size of the perborate to be granulated and the size of the granulates desired. This quantity decreases with increasing particle size of the initial perborate and increases with the size of the desired granulates. If it is merely desired to covert the perborate powder into granulates, in many cases, depending on the desired particle size of the granules, such small quantities of dispersion may be used that the granulate contains 95% and preferably 65% by weight NaBO .H O the balance of which consists of salt hydrate including possibly stabilizers. Generally, more dispersion is used so that there are present in the granulate, in addition to NaBO .H O .3H O, -40, and preferably, 20-30% by weight of salt hydrate. In many cases, it, however, may be of interest to prepare salt mixtures of lower perborate content which are intended for instance for mixing with other detergent components. In such case, the NaBO .H O .3H O content of the mixtures can dropto 15% by weight. The quantity of dispersion which is sprayed onto the perborate or perborate salt mixture to be granulated is for instance within the range of 5-45 and preferably 20-35% by weight referred to the granulate to be produced.

The quantity of water sprayed with the dispersion can exceed by a small amount the quantity of water which can be taken up by the mixture as water of crystallization in those cases in which the freshly formed granulate is cooled by air or conveyed in a stream of air since in these cases a certain amount of water evaporates. However, in all cases, it is advisable to regulate the water content of the granulate in such a manner that the water-vapor partial-pressure of the finished granulates is not greater than the Water-vapor partial-pressure of Na2CO3.7H20- The temperature of the dispersion to be sprayed should be higher than the melting point of the hydrates of the salts present in the suspension. If these salts form several stages of hydration, the temperature of the dispersion should be at least above the melting point of the hydrate of lowest melting point, but may, however, exceed the melting point of the hydrate of highest melting point. Pure N21 P O .1OI-I O melts at 79' C., the technical products 47 C. lower depending on their purity, while Na PO .l2H O melts at about 71 C. and Na B O .10I-I O is unstable above 58 C. 7

For the carrying out of the method of the invention,

there is used an apparatus which brings about a continuous change in surface of the salt to be granulated which is contained therein so that each particle is struck at least once by a drop of the sprayed dispersion solution during the time that it remains in the apparatus. The process is preferably carried out in rotating tubes, drums or plates, in which connection the axes of rotation of the tubes or drums may be horizontal or inclined and the plates themselves may be horizontal or inclined. The material to be granulated is charged into the apparatus and passes through same. The salt dispersion is sprayed onto the moving perborate mass, the nozzle as far as possible being of such a nature that the atomized solution of inorganic salts is distributed as uniformly as possible over a surface against which the moving perborate mass strikes. Furthermore, nozzles which send out a fan shaped jet have proven preferable. In this connection, the fan of atomized solution should preferably form a right angle with the direction of motion of the material.

The apparatus can be provided with stationary or with co-rotating inserts which, however, should extend extensively in the direction of motion of the material to be granulated so that as little friction as possible with the material passing through takes place, the continuous passage of the material is favored and contact of already formed granules with fresh or only partially granulated material is extensively avoided. Such inserts are for instance worms, scraper plates or deflector plates located in the direction of motion of the material along which the material slides. By means of these inserts, the result is obtained that the time of stay of each particle in the apparatus is as close as possible to the average time of stay of the entire material. The time of stay of the material can vary within wide limits as, for instance, between 5-200 seconds. However, a time of stay of 30- seconds has proved advisable. In this way, there is obtained a gentle treatment of the primarily formed, still deformable granules. In case of a longer time of stay, there takes place to be sure a formation of larger granules, but at the same time, there must be expected an undesired deformation of the still unhardened granules. For this reason, it is advisable either to adjust the operating conditions in such a manner that granules of the desired size are formed in one operation or else to subject an already granulated material to repeated granulation processes only after it is already solidified and preferably also cooled. Two or more consecutive granulation processes, however, should in general only be employed when a different salt is sprayed onto the granules in each granulation process.

If a cooling of the granules is desired, this can be effected in all known apparatus such as for instance cooling towers, cooling drums, etc. Cooling in parallel flow or counterflow of the material conveyed or eddied in a stream of air has proven particularly suitable. It is also possible to allow the material which is to be cooled to trickle down in a vertical pipe or tower and blow cold air against it at a speed which is somewhat less than the velocity of fall of the granules. In this way, the cooling of the granules can be combined with an air sifting.

An apparatus for the carrying out of the process of the invention is shown in Figure 1. The perborate which is to be granulated is present in the storage vessel .t and passes via the metering device 2 into the hopper 3 which conduct it to the granulating device 4 which is represented here as an oblique rotating plate. In the storage vessel 5, there is contained the calcined salt to be used possibly as auxiliary agent in the granulation, the said salt being conducted via the metering device 6 into the hopper 3 where it mixes with the perborate. In the vessel '7, there is a preferably hot solution of the salt present in the storage vessel 5 or of another salt which crystallizes with the inclusion of water of crystallization and an undissolved salt for using a thinly liquid dispersion. The

'5 vessel 7 may be placed under pressure by a gas via the conduct 8 and the reducing valve 9, so that the solution passes through the line 10, which can be provided with heating means 11 to the nozzle 12 and from there is sprayed onto the granulating plate or tray 4. For the purposes of the invention, it has been found advantageous to provide the vessel 7 with an agitator and/ or to replace the pressure vessel 7 by a vessel having no pressure and to pump the thinly liquid dispersion by means of a screw pump to the nozzle 12. The granulating plate 4 is shown in greater detail in Figures 2ac. The granulated material passes over the rim of the plate into the hopper 13 and from there into the pipeline 14 and into vessel 15. Into this vessel 15, air is forced by fan 16 via conduit 17 and throttle valve 18. A part of this air flows in the pipeline 14 in countercurrent to the granulate which has just been formed at such a speed that the velocity of drop of the granulate in conduit 14 is greatly reduced, in which connection, the granulate is simultaneously cooled. The granulate falls to the bottom of container and is conveyed at the lower funnel-shaped part of vessel 15 by the remaining part of the air forced into said vessel into thedrop-pipe 19 which is connected with the lower part of the riser pipe 20. Through the lower open end of the riser pipe 20 air is drawn in from the fan 27 at such a velocity that the entire perborate is raised through this riser pipe into the separator 21. The air leaves the separator through the conduit 22 and passes to the cyclone 23 where the fine ungranulated or insufficiently granulated particles entrained by the stream of air are separated and conveyed back to the hopper 3 via conduit 24. The stream of air is drawn out of the cyclone 23 via the 'fan 27, the throttle valve 26 and the conduit 25. The

perborate which has separated out in container 21 leaves the separator at its lower opening and drops onto the shaking screen 28; the material which passes through the shaking screen is the granulate of the desired particle size and is discharged through conduit 29. The coarsely granular material remaining on screen 28 is carefully comminuted in the mill 30. The conduit 31 conveys the material emerging from the mill under the vacuum prevailing in the separator 21 back to the separator where the dust particles are removed.

Figures 2a to 2c show the granulating plate 4 of Figure 1 in more detail, Figure 2a being a projection of the granulating device on a plane parallel to the granulating plate 40. Figure 2b shows the granulating device in section through a vertical plane coinciding with the axis of rotation of plate 40, while Figure 2c shows the apparatus in perspective.

Referring to Figures 2a2c, the granulation takes place on the inclined rotatable granulating plate 40 provided with a rim 52, the said plate being driven by a variable geared motor 41. The geared motor 41 rests on a block 37 and is swingably supported together with the latter on a base 42 via a pin 43. A locking device 44 makes it possible to fix the desired angle of inclination. The material to be granulated is conducted via the hopper 3 and the charging pipe 46 onto the plate 40 where it is moved over the surface of the plate by the rotation thereof. The main portion of the material to be granulated collects at the rim of the plate at a place which is further from or closer to the lowest point of the plate depending on the quantity of the material and the speed of rotation of the plate, and forms there a mass 39 which is continuously moved about. A part of the material is carried along in the direction of motion at the rim of the plate and then drops from the upper rim back over the inclined plate to the lower rim of the plate. The quantity of material which is carried along in this manner and the width of the surface taken up by the backward falling material can be regulated by the speed of regulation and the inclination of the plate. The backward moving material trickles in the form of parallel lines or curves 47 which are similar to each other back over the inclined '6 plate and combines with the mass 39 present at the lower rim of the plate. In this way there is obtained a continuous changing of the surface of the material to be granulated, present on the plate.

Against the material trickling down in accordance with the lines 47, there is now directed the preferably fan shaped jet 48 of atomized solution which is fed to the nozzle 49 via a conduit 50 provided with the accompanying heating coil 51. If a fan-shaped nozzle jet is employed, it is advisable to adjust it in such a manner that the lines 47 form a right angle with the generatriX of the jet 48. The spray particles now come into contact with the mass 39 of the material to be granulated and have an opportunity there to agglomerate with other particles of the material. It may happen that sprayed particles stick to the rim 52 of the plate 40. These particles are scraped off from the rim 52 of the plate by a stationary scraper 53 which is connected by the holding device 38 with the bearing block 37 of motor 41. The scraper 53 is developed as a guide plate, the shape of which is identical to the trajectory of the outermost lines 47. In this way, the particles of material are brought into the desired direction of motion without strong friction. As a result of this, there is obtained behind the scraper 53 a surface which is free of material and onto which the starting material to be granulated drops. The shape of lines 47 is dependent inter alia on the particle size of the material falling along these lines. Since the coarser particles have narrower trajectoriw, the granulates move to the left corresponding to the increasing particle size out from the region of the nozzle jet 48 and finally fall, following the arrows 54, into the hopper 55 where they are further worked in the manner described above.

The granulation can also be effected in a rotating drum which is shown in Figures 3a and 3b. The material to be granulated is conducted via the hopper 60 and the pipe 61 into the drum 62. There it is partially raised by the rotating pipe in which it forms the continuously moving mass 58. The stripper 64 prevents too extensive a lifting of the material aswell as a baking of the sprayed particles to the wall of the drum. The dispersion solution used for the spraying is introduced through the pipe 56 into the inside of drum 62 and is converted there by the nozzles 57 into the spray jets 63. The spraying need not be effected over the entire length of the pipe. If only the central region 66 of the pipe is to be used for the spraying, there takes place in the upper region 65 where the material is introduced a mixing of the components to be granulated while in the lower region 67 of the pipe, the particles which have already been sprayed with the dispersion solution have an opportunity to bake together with other particles of the mass 58 to be granulated. The graunlates emerge from the drum 62 along the path indicated by the arrow 68.

The following example is given by way of illustration and not limitation:

EXAMPLE For the carrying out of the process, there was used an apparatus such as shown in Figure 1, equipped with a granulating plate such as shown in Figures 2a-2c. Dry perborate which contained about 95% of the water of crystallization corresponding to the formula was continuously conducted onto the granulating plate, the size inclination and speed of rotation of which were so regulated that the average time of stay of the perborate was 30-40 seconds. In a few tests, dry anhydrous sodium pyrophosphate was added to the perborate. Onto the perborate or perborate-pyrophosphate mixture which trickled down along the lines 47 over the plate, there was sprayed by means of a nozzle 49 a dispersion of 40 parts by weight Na P O in 60 parts by weight Water of -85 C. (dispersion of 22 parts by weight Na P O in 78 parts by weight saturated solution). The spray jet had a fan shape. The contact line of the fan on the surface of the plate was approximately at right angles to the flow .lines 47 of the perborate particles. 600 cubic meters per hour of air of 15-25 C. were passed in countercurrent in conduit 14 to the granulate trickling down from the plate. The time of stay of the granulates in the conduit was about seconds. The material passed via conduit 19 together with a part of the air from fan 16 into the riser pipe 20 in which the material was raised with an air velocity of about 8-10 meters per second and a velocity of its own of 1.5-4 meters per second. After the separation of the finely-pulverized fraction (about 25 kg./hr.) in the separator 21 and cyclone 23, which was fed to the hopper 3, and the separation of the oversize (15 kg./hr.) in the shaking screen 28 (mesh aperture 2.5 mm.), the granulate was obtained at the screen outlet 29.

The following tables indicate the quantities of starting material used in the experiments, thequantities of granulate obtained, the composition of the graunlates and the screen analyses of the starting materials and of the granulates.

Quantities of starting material and granulate Screen analysis of the starting materials and of the granulate Percenta e of the Fractions in Weight, percent; Mesh Aperture of the Screens in mm.

Pyrophos- Granulates Perborate phate According to Exp. 1-3

0. 2 21. 4 0.3 22. 7 1. 13. i 8. 3 11. O 54. 8 23. 1 l5. 9 5. 2 10. 4 3. 2

The size of the granulates to be produced in accordance with the process of the invention can vary within very wide limits, depending on the existing requirements. In g neral, granulates of a particle size of above 5 mm. are required only in special cases. For use in detergents, granulates of a particle size of 2-0.3 mm. in general, constituting at least 50% by weight of the total granulate.

A dry granular detergent is made by spraying an aqueous paste of the said detergent in hot air. The screen analysis of the detergent is the following:

Percentage of the fractions in weight, percen t Mesh aperture of the screen in mm.

parts by weight of this granular detergent are mixed with 20 parts by weight of a granular perborate obtained according tothe Example 1 or 2. The mixture does not separate in handling transportation and storage as it does when the perborate is used in the not agglomerated state.

The chemical composition of the detergent obtained by spraying was the following one:

10% by weight alkylbenzenesulfonate' alkyl=C -C 8% by weight oleylsulfate 12% by weight Na CO 17% by weight Na P O Weight N33P5010 6% by weight MgSiO 8% by weight Na O.3.3SiO

18% by weight Na SQ,

0.04% by weight fluorescent Water up to by weight.

As avoiding of separation is a matter of grain size and not of chemical composition, detergents of any chemical composition may be used instead of the above.

If the granular perborates should contain stabilizing agents these should be present in an amount of 0.5-2() percent by weight, calculated-on the NaBO .H O present in the salt mixture.

While the invention has been described in detail with reference to the specific embodiments shown, various changes and modifications will become apparent to the skilled artisan, which fall within the spirit of the invention and the'scope of the appended claims.

We'claim:

1. A process for the production of granular salt mix tures containing perborates which comprises moving a finely divided water-soluble perborate on a support surface for contact between the individual divided particles while spraying the perborate with a thinly liquid dispersion of an undissolved salt capable of crystallizing with the inclusion of water of crystallization in an aqueous solution of'a' salt capable of crystallizing with the inclusion of water of crystallization at a temperature above the melting temperature of the lowest melting component of said undissolved salt, the contact of the perborate'and dispersion being effected at a temperature allowing crystallization of the dispersion and salt solution and agglomeration between individual divided perborate particles, said salt solution'spray containing an amount of water not substantially in excess of the amount of water capable of being bound as water of crystallization by the salt mixture formed, the quantity of dispersion which is sprayed onto the perborate to be granulated being in the range of 5-45% by weight based on the granulate to be produced, and recovering the granular agglomerated perborate particle salt mixture formed containing substantially all of the water sprayed as water of crystallization.

2. A process, according to claim 1, in which said perborate is a sodium perborate.

3-. A process,- according to claim 1, in which said undissolved salt is a salt which is capable of crystallizing with the inclusion of water of crystallization into crystals having a lower solubility than soda.

4. A process, according to claim 1, which includes cooling the mixture after said spraying.

5. A process, according to claim 1, in which said finely divided perborate is sprayed while being rotated in a rotating, granulating device.

6. A process, according to claim 1, in which said perborate is admixed with a solid, divided inorganic salt prior to said spraying.

7. A process, according to claim 1, in which said spraying is effected in the presence of a stabilizer for the perborate.

8. A process, according to claim 1, in which said aqueous solution of a salt is a saturated salt solution containing less than 50% of undissolved salt.

9. A process according to claim 1, in which the quantity of dispersion which is to be sprayed onto the perborate to be granulated is in the range of 20-35% by weight based on the granulate to be produced.

10. A process, according to claim 2, in which said undissolved salt in said dispersion is a sodium phosphate and in which said aqueous solution of a salt is a saturated sodium phosphate solution.

11. A process, according to claim 6, in which said solid divided inorganic salt is the same salt as the salt forming said dispersion and aqueous salt solution.

12. A process, according to claim 8, in which said salt solution contains less than 30% by weight of said undissolved salt.

13. A process, according to claim 10, in which said aqueous salt solution spray contains a quantity of water 19 not in excess of the amount capable of producing a salt mixture with a vapor pressure equivalent to the vapor pressure of Na CO .7H O.

14. A process, according to claim 11, in which said 5 solid divided inorganic salt is a calcined salt.

References Cited in the file of this patent UNITED STATES PATENTS 10 2,308,992 Mertens Jan. 19, 1943 2,524,394 Madorsky Oct. 3, 1950 2,706,178 Young Apr. 12, 1955 2,763,618 Hendrix Sept. 18, 1956 2,765,239 Sicgrist Oct. 2, 1956 15 2,767,146 Bonewitz et al. Oct. 16, 1956 

1. A PROCESS FOR THE PRODUCTION OF GRANULAR SALT MIXTURES CONTAINING PERBORATES WHICH COMPRISES MOVING A FINELY DIVIDED WATER-SOLUBLE PERBORATE ON A SUPPORT SURFACE FOR CONTACT BETWEEN THE INDIVIDUAL DIVIDED PARTICLES WHILE SPRAYING THE PERBORATE WITH A THINLY LIQUID DISPERSION OF AN UNDISSOLVED SALT CAPABLE OF CRYSTALLIZING WITH THE INCLUSION OF WATER OF CRYSTALLIZATION IN AN AQUEOUS SOLUTION OF A SALT CAPABLE OF CRYSTALLIZING WITH THE INCLUSION OF WATER OF CRYSTALLIZATION AT A TEMPERATURE ABOVE THE MELTING TEMPERATURE OF THE LOWEST MELTING COMPONENT OF SAID UNDISSOLVED SALT, THE CONTACT OF THE PERBORATE AND DISPERSION BEING EFFECTED AT A TEMPERATURE ALLOWING CRYSTALLIZATION OF THE DISPERSION AND SALT SOLUTION AND AGGLOMERATION BETWEEN INDIVIDUAL DIVIDED PERBORATE PARTICLES, SAID SALT SOLUTION SPRAY CONTAINING AN AMOUNT OF WATER NOT SUBSTANTIALLY IN EXCESS OF THE AMOUNT OF WATER CAPABLE OF BEING BOUND AS WATER OF CRYSTALLIZATION BY THE SALT MIXTURE FORMED, THE QUANTITY OF DISPERSION WHICH IS SPRAYED ONTO THE PERBORATE TO BE GRANULATED BEING IN THE RANGE OF 5-45% BY WEIGHT BASED ON THE GRANULATE TO BE PRODUCED, AND RECOVERING THE GRANULAR AGGLOMERATED PERBORATE PARTICLE SALT MIXTURE FORMED CONTAINING SUBSTANTIALLY ALL OF THE WATER SPRAYED AS WATER OF CRYSTALLIZATION. 